Global oil crises such as depletion of petroleum and natural gas and instability of supply and demand systems are being created. Restrictions on the use of fossil fuels as energy sources are becoming more visible to protect ecosystems from climate change and environmental destruction or the like.
As a result, all countries of the world are making efforts not only to develop new and renewable energy but also to increase the efficiency of existing thermal power generation and to make eco-friendly inventories. Biological energy production technologies using photosynthetic microorganisms or the like are also attracting attention.
In recent years, research on the use of photosynthetic microorganisms has focused on the production of biofuels for transportation, due to the increase in prices of cereal resources due to the production of biofuels and concerns about food resources. In accordance with this, application researches such as improvement in microorganisms, a reactor, system research or the like in addition to basic researches on genomes and genes of photosynthetic microorganisms or the like have been conducted on a large scale.
The photosynthetic microorganisms can grow using water, carbon dioxide and sunlight, and can be cultivated anywhere in wastelands, coasts, and oceans, such that they do not compete with existing land crops in terms of land or space. The photosynthetic microorganisms accumulate large amounts of lipids (up to 70%) in a living body according to culture conditions and their oil (lipid) production per unit area is 50-100 times higher than typical edible crops such as soybeans, such that they may have very high functionality as biodiesel. The biodiesel, which is produced using the photosynthetic microorganisms such as microalgae as a raw material, can greatly reduce emission of pollutants such as fine dust and sulfur compounds as compared with the conventional diesel fuel and therefore is suitable as fuel for an eco-friendly car.
In order to efficiently produce the photosynthetic microorganisms, development of high-efficiency photobioreactors and high concentration culture techniques has been attempted, and a method for culturing photosynthetic microorganisms such as microalgae can be roughly classified into a method using an outdoor culture method and a method using a photobioreactor.
An example of the outdoor culture method may include a water channel type in which the medium is circulated in a pond shape or an outer wheel shape. The outdoor culture method has less installation cost and operation cost, but has a disadvantage in that it has difficulty in performing the high concentration culture and may be easily contaminated by other microorganisms to increase withdraw cost of photosynthetic products.
Therefore, it becomes possible to produce high value added materials such as biofuels, pharmaceuticals, health foods, and feeds using the photosynthetic microorganisms. In particular, as a high concentration mass culturing technique of photosynthetic microorganisms is essentially required for a biological carbon dioxide immobilization process, a demand for a photobioreactor having high culture efficiency is increasing.
Korean Patent No. 10-0283026 which is currently developed domestically discloses a form of a photobioreactor in which an aerial photobioreactor uses a cylindrical inner conduit as a luminous body and Korean Patent Laid-open Publication No. 10-2003-0018196 discloses a cylinder type photobioreactor in which an agitator is used as a luminous body.
Isolation of high productivity microalgae and establishment of optimal production conditions by the photobioreactors are essential for increasing biomass productivity. The productivity of microalgae greatly depends on conditions of a quantity of light, temperature and carbon dioxide. The isolation of the microalgae having high productivity and the optimal culture conditions should take into account the essential requirements of the photosynthesis, but it is not easy to control the conditions of the quantity of light, the temperature, and the carbon dioxide in the laboratory environment.
Accordingly, there is a need for a photobioreactor capable of establishing optimal production conditions.